JPS62173265A - Thermal print head - Google Patents

Abstract

PURPOSE:To make the lowering in resistance of a common lead possible by a simple structure, by installing the common lead on the surface of another glaze layer provided parallel to the heating part glaze layer on the surface of a substrate. CONSTITUTION:Another glaze layer 7 is provided parallel to a glaze layer 2 on the surface of a substrate 1 between the glaze layer 2 and the end edge 1A of the substrate 1. Further, a common lead 5 is installed over the surface of this glaze layer 7. Because the resistance film 3A for forming a heating part 3 is practically formed from the surface of the glaze layer 2 to the end edge 1A side, the common lead 5 is no provided as to be overlapped on the surface of this resistance film. The common lead 5 extends from the end part of the line of the heating part 3 along the side edge 1B of the substrate 1 further toward the another end edge of the substrate 1 in the same way as an individual lead 4. Because most of the common lead part 5A parallel to the line of the heating part 3 exist on the surface of the glaze layer 7, whereby the resistance value along its line direction becomes smaller than that provided usually on the surface of a ceramics substrate.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a thermal print head.

(Prior art) In a thermal print head, a glaze layer is provided on the surface of a ceramic substrate, and a large number of heat generating parts made of resistors are installed in a straight line on the surface of this glaze layer. It is already well known to have individual leads at one end and a common lead at the other end.

FIG. 3 shows a cross-sectional view of a conventional head of this type, in which 1 is a ceramic substrate, 2 is a glaze layer provided on its surface, and a large number of heat generating parts 3 are formed in a layered manner on the surface. and - located along a straight line. Actually, a resistive film 3A is uniformly formed on the surface, and a part of the resistive film 3A is used as the heat generating part 3.

4 is an individual lead provided at one end of each heat generating portion 3; 5 is a common lead commonly provided at the other end; 6
is a protective layer.

The common lead 5 is connected to one terminal of a power source for heat generation, and the individual leads 4 are selectively connected to the other terminal of the power source to selectively generate heat from each heat generating part, This performs the required printing.

By the way, this row of heat generating parts 3 is connected to one edge IA (
See Figure 2. same as below. ), and in that case, the row of heat generating parts 3 is made parallel to the above-mentioned one edge IA of the substrate 1, the common lead 5 is drawn out to the edge IA side, and This is routed to one or both ends of the row of heat generating parts 3, and is extended from there toward the other edge of the board in the same way as the individual leads 4.

By the way, according to such a configuration, the common lead 5 is routed along the direction parallel to the row of heat generating parts 3 toward the end of the row, and therefore is formed to be longer by the length of the route. . Therefore, due to the resistance of the common lead 5, the resistance of the common lead 5 acts more strongly from the end of the column toward the center of the column.

Due to the action of this resistance, the voltage drop along the row direction of the heat generating parts 3 increases, and the heat generating parts 3 located closer to the center of the row generate more heat than the heat generating parts 3 located at the ends of the row. becomes smaller. Therefore, when actually printed, the density on the center side becomes lighter than on the edge sides, resulting in density unevenness.

In order to improve this problem, the common lead portion 5A along the row of the heat generating portions 3 should be manufactured so that the resistance thereof is as small as possible. For this reason, in the past, there have been devices in which the common lead portion 5A has been made thicker by forming it in two layers, but forming a film by coating two layers in this way is an extremely troublesome task, and it is difficult to do so. Not desirable.

(Problems to be Solved by the Invention) It is an object of the present invention to reduce the resistance of a common lead that is routed along a row of heat generating parts to the end of the row with a simple configuration.

(Means for Solving the Problems) This invention provides a glaze layer on the surface of a substrate, heat generating parts are installed on the surface of the glaze layer, and an individual lead is connected to one end of each heat generating part, and an individual lead is connected to the other end of each heat generating part. In the thermal print head, a common lead is provided in common at the end of the substrate, and the common lead is routed along the direction of the row of the heat generating parts toward the end of the row. It is characterized in that it is provided on the surface of a separate glaze layer provided parallel to the glaze layer.

(Function) In the conventional configuration, most of the common lead is formed on the surface of the ceramic substrate, but in this invention, most of the common lead is formed on the surface of the newly provided glaze layer. did. Generally, the surface of ceramics has numerous minute irregularities and small holes. Therefore, when a film-like layer, for example, a layer for leads, is formed on the surface, the thickness of the film becomes non-uniform, and therefore the resistance value thereof becomes relatively large.

However, the surface of the glaze layer is smoother than that of ceramic, and therefore the thickness of the film formed on the surface is uniform. Therefore, the resistance value is smaller than that of a film formed on a ceramic surface, even if the film is made of the same material. For example, although it varies depending on the ceramic used, the type of glaze, and the printing condition of the film, it has been confirmed that the resistance value is about 20% lower on the surface of the glaze layer than on the surface of the ceramic layer, even if the layer is made of the same material. ing.

If the common lead is formed on the surface of the newly provided glaze layer in this way, it will exhibit a lower resistance value than when it is formed on the ceramic surface as in the past. The resistance value is almost constant. This reduces the voltage drop along the row of heat generating parts.

The amount of heat generated from each heat generating portion becomes almost uniform, and unevenness in color density can thereby be avoided.

(Example) An embodiment of the invention will be described with reference to FIGS. 1 and 2.

Note that parts given the same reference numerals as in FIG. 3 indicate the same or corresponding parts. According to the invention, a separate glaze layer 7 is provided on the surface of the substrate 1, parallel to the glaze layer 2, between the glaze layer 2 and the edge IA of the substrate 1. If this is provided together with the glaze layer 2, there is no need to add a special process.

A common lead 5 is placed across the surface of this glaze layer 7.
will be established. 5A indicates a common lead portion parallel to the rows of heat generating parts 3. Actually, the resistive film 3 for forming the heat generating part 3
Since A is formed from the surface of glaze layer 2 to the edge IA side, common ground 5 is provided so as to overlap the surface of this resistive film.

The common lead 5 extends from the end of the row of heat generating parts 3 to the side a of the substrate 1.
1B, and further extends toward the other edge of the substrate 1 in the same way as the individual leads 4. This configuration is not particularly different from the conventional configuration.

With this configuration, since most of the common lead portions 5A parallel to the rows of the heat generating parts 3 are on the surface of the glaze layer 7, the resistance value along the row direction is set on the surface of the ceramic substrate as in the conventional case. become smaller than something. Therefore, since the voltage drop of the common REIT along the column direction becomes small, unevenness in the color density of each heat generating section 3 can be sufficiently avoided.

(Effects of the Invention) As detailed above, according to the present invention, even when the common lead is provided parallel to the row of heat generating parts, the resistance value of the common lead portion along the row direction can be made smaller than before. As a result, the voltage drop in this portion is reduced, so that it is possible to sufficiently avoid uneven color development due to the heat generating portions along the two-column direction.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a plan view thereof, and FIG. 3 is a sectional view showing a conventional example. DESCRIPTION OF SYMBOLS 1...Substrate, 2...Glaze layer, 3...Heating part,
4...Individual lead, 5...Common lead, 5A...
common lead part, 7... glaze layer,

Claims (1)

[Claims] A glaze layer is provided on the surface of the substrate, a heat generating part is provided on the surface of the glaze layer, an individual lead is provided at one end of each heat generating part, and a common lead is provided at the other end of the heat generating part. In a thermal print head in which a common lead is routed along the row direction of the heat generating parts toward the end of the row, the common lead is formed on a separate glaze layer provided on the surface of the substrate in parallel to the glaze layer. A thermal print head installed on the surface.